Albion need a tenth away win of the season if they are to get to Wembley after their play-off dreams suffered a setback tonight.
The Seagulls let slip an early lead to lose 2-1 to Derby in the first leg of their semi-final.
Jesse Lingard fired them ahead on 18 minutes after good work by Inigo Calderon down the right.
Chris Martin levelled with a penalty after Matt Upson fouled Craig Forsyth.
Then Martin’s blast in first-half stoppage time crashed back off the bar and bounced off the unfortunate Tomasz Kuszczak for what proved to be the winner.
Albion gave it their all in the second half but found man-of-the-match Lee Grant in inspired form in the Derby goal.
Grant turned a Leo Ulloa volley on to the bar, produced a fine parry from Lingard and then topped that with a tip over from Stephen Ward’s blast.
Albion also looked to have good penalty claims for holding by Jake Buxton on Ulloa.
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